nbd/server.c

   1 /*
   2  *  Copyright (C) 2005  Anthony Liguori <anthony@codemonkey.ws>
   3  *
   4  *  Network Block Device Server Side
   5  *
   6  *  This program is free software; you can redistribute it and/or modify
   7  *  it under the terms of the GNU General Public License as published by
   8  *  the Free Software Foundation; under version 2 of the License.
   9  *
  10  *  This program is distributed in the hope that it will be useful,
  11  *  but WITHOUT ANY WARRANTY; without even the implied warranty of
  12  *  MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE.  See the
  13  *  GNU General Public License for more details.
  14  *
  15  *  You should have received a copy of the GNU General Public License
  16  *  along with this program; if not, see <http://www.gnu.org/licenses/>.
  17  */
  18
  19 #include "qemu/osdep.h"
  20 #include "qapi/error.h"
  21 #include "nbd-internal.h"
  22
  23 static int system_errno_to_nbd_errno(int err)
  24 {
  25     switch (err) {
  26     case 0:
  27         return NBD_SUCCESS;
  28     case EPERM:
  29     case EROFS:
  30         return NBD_EPERM;
  31     case EIO:
  32         return NBD_EIO;
  33     case ENOMEM:
  34         return NBD_ENOMEM;
  35 #ifdef EDQUOT
  36     case EDQUOT:
  37 #endif
  38     case EFBIG:
  39     case ENOSPC:
  40         return NBD_ENOSPC;
  41     case EINVAL:
  42     default:
  43         return NBD_EINVAL;
  44     }
  45 }
  46
  47 /* Definitions for opaque data types */
  48
  49 typedef struct NBDRequest NBDRequest;
  50
  51 struct NBDRequest {
  52     QSIMPLEQ_ENTRY(NBDRequest) entry;
  53     NBDClient *client;
  54     uint8_t *data;
  55     bool complete;
  56 };
  57
  58 struct NBDExport {
  59     int refcount;
  60     void (*close)(NBDExport *exp);
  61
  62     BlockBackend *blk;
  63     char *name;
  64     off_t dev_offset;
  65     off_t size;
  66     uint32_t nbdflags;
  67     QTAILQ_HEAD(, NBDClient) clients;
  68     QTAILQ_ENTRY(NBDExport) next;
  69
  70     AioContext *ctx;
  71
  72     Notifier eject_notifier;
  73 };
  74
  75 static QTAILQ_HEAD(, NBDExport) exports = QTAILQ_HEAD_INITIALIZER(exports);
  76
  77 struct NBDClient {
  78     int refcount;
  79     void (*close)(NBDClient *client);
  80
  81     NBDExport *exp;
  82     QCryptoTLSCreds *tlscreds;
  83     char *tlsaclname;
  84     QIOChannelSocket *sioc; /* The underlying data channel */
  85     QIOChannel *ioc; /* The current I/O channel which may differ (eg TLS) */
  86
  87     Coroutine *recv_coroutine;
  88
  89     CoMutex send_lock;
  90     Coroutine *send_coroutine;
  91
  92     bool can_read;
  93
  94     QTAILQ_ENTRY(NBDClient) next;
  95     int nb_requests;
  96     bool closing;
  97 };
  98
  99 /* That's all folks */
 100
 101 static void nbd_set_handlers(NBDClient *client);
 102 static void nbd_unset_handlers(NBDClient *client);
 103 static void nbd_update_can_read(NBDClient *client);
 104
 105 static gboolean nbd_negotiate_continue(QIOChannel *ioc,
 106                                        GIOCondition condition,
 107                                        void *opaque)
 108 {
 109     qemu_coroutine_enter(opaque);
 110     return TRUE;
 111 }
 112
 113 static ssize_t nbd_negotiate_read(QIOChannel *ioc, void *buffer, size_t size)
 114 {
 115     ssize_t ret;
 116     guint watch;
 117
 118     assert(qemu_in_coroutine());
 119     /* Negotiation are always in main loop. */
 120     watch = qio_channel_add_watch(ioc,
 121                                   G_IO_IN,
 122                                   nbd_negotiate_continue,
 123                                   qemu_coroutine_self(),
 124                                   NULL);
 125     ret = read_sync(ioc, buffer, size);
 126     g_source_remove(watch);
 127     return ret;
 128
 129 }
 130
 131 static ssize_t nbd_negotiate_write(QIOChannel *ioc, void *buffer, size_t size)
 132 {
 133     ssize_t ret;
 134     guint watch;
 135
 136     assert(qemu_in_coroutine());
 137     /* Negotiation are always in main loop. */
 138     watch = qio_channel_add_watch(ioc,
 139                                   G_IO_OUT,
 140                                   nbd_negotiate_continue,
 141                                   qemu_coroutine_self(),
 142                                   NULL);
 143     ret = write_sync(ioc, buffer, size);
 144     g_source_remove(watch);
 145     return ret;
 146 }
 147
 148 static ssize_t nbd_negotiate_drop_sync(QIOChannel *ioc, size_t size)
 149 {
 150     ssize_t ret, dropped = size;
 151     uint8_t *buffer = g_malloc(MIN(65536, size));
 152
 153     while (size > 0) {
 154         ret = nbd_negotiate_read(ioc, buffer, MIN(65536, size));
 155         if (ret < 0) {
 156             g_free(buffer);
 157             return ret;
 158         }
 159
 160         assert(ret <= size);
 161         size -= ret;
 162     }
 163
 164     g_free(buffer);
 165     return dropped;
 166 }
 167
 168 /* Basic flow for negotiation
 169
 170    Server         Client
 171    Negotiate
 172
 173    or
 174
 175    Server         Client
 176    Negotiate #1
 177                   Option
 178    Negotiate #2
 179
 180    ----
 181
 182    followed by
 183
 184    Server         Client
 185                   Request
 186    Response
 187                   Request
 188    Response
 189                   ...
 190    ...
 191                   Request (type == 2)
 192
 193 */
 194
 195 static int nbd_negotiate_send_rep(QIOChannel *ioc, uint32_t type, uint32_t opt)
 196 {
 197     uint64_t magic;
 198     uint32_t len;
 199
 200     TRACE("Reply opt=%" PRIx32 " type=%" PRIx32, type, opt);
 201
 202     magic = cpu_to_be64(NBD_REP_MAGIC);
 203     if (nbd_negotiate_write(ioc, &magic, sizeof(magic)) != sizeof(magic)) {
 204         LOG("write failed (rep magic)");
 205         return -EINVAL;
 206     }
 207     opt = cpu_to_be32(opt);
 208     if (nbd_negotiate_write(ioc, &opt, sizeof(opt)) != sizeof(opt)) {
 209         LOG("write failed (rep opt)");
 210         return -EINVAL;
 211     }
 212     type = cpu_to_be32(type);
 213     if (nbd_negotiate_write(ioc, &type, sizeof(type)) != sizeof(type)) {
 214         LOG("write failed (rep type)");
 215         return -EINVAL;
 216     }
 217     len = cpu_to_be32(0);
 218     if (nbd_negotiate_write(ioc, &len, sizeof(len)) != sizeof(len)) {
 219         LOG("write failed (rep data length)");
 220         return -EINVAL;
 221     }
 222     return 0;
 223 }
 224
 225 static int nbd_negotiate_send_rep_list(QIOChannel *ioc, NBDExport *exp)
 226 {
 227     uint64_t magic, name_len;
 228     uint32_t opt, type, len;
 229
 230     TRACE("Advertising export name '%s'", exp->name ? exp->name : "");
 231     name_len = strlen(exp->name);
 232     magic = cpu_to_be64(NBD_REP_MAGIC);
 233     if (nbd_negotiate_write(ioc, &magic, sizeof(magic)) != sizeof(magic)) {
 234         LOG("write failed (magic)");
 235         return -EINVAL;
 236      }
 237     opt = cpu_to_be32(NBD_OPT_LIST);
 238     if (nbd_negotiate_write(ioc, &opt, sizeof(opt)) != sizeof(opt)) {
 239         LOG("write failed (opt)");
 240         return -EINVAL;
 241     }
 242     type = cpu_to_be32(NBD_REP_SERVER);
 243     if (nbd_negotiate_write(ioc, &type, sizeof(type)) != sizeof(type)) {
 244         LOG("write failed (reply type)");
 245         return -EINVAL;
 246     }
 247     len = cpu_to_be32(name_len + sizeof(len));
 248     if (nbd_negotiate_write(ioc, &len, sizeof(len)) != sizeof(len)) {
 249         LOG("write failed (length)");
 250         return -EINVAL;
 251     }
 252     len = cpu_to_be32(name_len);
 253     if (nbd_negotiate_write(ioc, &len, sizeof(len)) != sizeof(len)) {
 254         LOG("write failed (length)");
 255         return -EINVAL;
 256     }
 257     if (nbd_negotiate_write(ioc, exp->name, name_len) != name_len) {
 258         LOG("write failed (buffer)");
 259         return -EINVAL;
 260     }
 261     return 0;
 262 }
 263
 264 static int nbd_negotiate_handle_list(NBDClient *client, uint32_t length)
 265 {
 266     NBDExport *exp;
 267
 268     if (length) {
 269         if (nbd_negotiate_drop_sync(client->ioc, length) != length) {
 270             return -EIO;
 271         }
 272         return nbd_negotiate_send_rep(client->ioc,
 273                                       NBD_REP_ERR_INVALID, NBD_OPT_LIST);
 274     }
 275
 276     /* For each export, send a NBD_REP_SERVER reply. */
 277     QTAILQ_FOREACH(exp, &exports, next) {
 278         if (nbd_negotiate_send_rep_list(client->ioc, exp)) {
 279             return -EINVAL;
 280         }
 281     }
 282     /* Finish with a NBD_REP_ACK. */
 283     return nbd_negotiate_send_rep(client->ioc, NBD_REP_ACK, NBD_OPT_LIST);
 284 }
 285
 286 static int nbd_negotiate_handle_export_name(NBDClient *client, uint32_t length)
 287 {
 288     int rc = -EINVAL;
 289     char name[NBD_MAX_NAME_SIZE + 1];
 290
 291     /* Client sends:
 292         [20 ..  xx]   export name (length bytes)
 293      */
 294     TRACE("Checking length");
 295     if (length >= sizeof(name)) {
 296         LOG("Bad length received");
 297         goto fail;
 298     }
 299     if (nbd_negotiate_read(client->ioc, name, length) != length) {
 300         LOG("read failed");
 301         goto fail;
 302     }
 303     name[length] = '\0';
 304
 305     TRACE("Client requested export '%s'", name);
 306
 307     client->exp = nbd_export_find(name);
 308     if (!client->exp) {
 309         LOG("export not found");
 310         goto fail;
 311     }
 312
 313     QTAILQ_INSERT_TAIL(&client->exp->clients, client, next);
 314     nbd_export_get(client->exp);
 315     rc = 0;
 316 fail:
 317     return rc;
 318 }
 319
 320
 321 static QIOChannel *nbd_negotiate_handle_starttls(NBDClient *client,
 322                                                  uint32_t length)
 323 {
 324     QIOChannel *ioc;
 325     QIOChannelTLS *tioc;
 326     struct NBDTLSHandshakeData data = { 0 };
 327
 328     TRACE("Setting up TLS");
 329     ioc = client->ioc;
 330     if (length) {
 331         if (nbd_negotiate_drop_sync(ioc, length) != length) {
 332             return NULL;
 333         }
 334         nbd_negotiate_send_rep(ioc, NBD_REP_ERR_INVALID, NBD_OPT_STARTTLS);
 335         return NULL;
 336     }
 337
 338     if (nbd_negotiate_send_rep(client->ioc, NBD_REP_ACK,
 339                                NBD_OPT_STARTTLS) < 0) {
 340         return NULL;
 341     }
 342
 343     tioc = qio_channel_tls_new_server(ioc,
 344                                       client->tlscreds,
 345                                       client->tlsaclname,
 346                                       NULL);
 347     if (!tioc) {
 348         return NULL;
 349     }
 350
 351     TRACE("Starting TLS handshake");
 352     data.loop = g_main_loop_new(g_main_context_default(), FALSE);
 353     qio_channel_tls_handshake(tioc,
 354                               nbd_tls_handshake,
 355                               &data,
 356                               NULL);
 357
 358     if (!data.complete) {
 359         g_main_loop_run(data.loop);
 360     }
 361     g_main_loop_unref(data.loop);
 362     if (data.error) {
 363         object_unref(OBJECT(tioc));
 364         error_free(data.error);
 365         return NULL;
 366     }
 367
 368     return QIO_CHANNEL(tioc);
 369 }
 370
 371
 372 static int nbd_negotiate_options(NBDClient *client)
 373 {
 374     uint32_t flags;
 375     bool fixedNewstyle = false;
 376
 377     /* Client sends:
 378         [ 0 ..   3]   client flags
 379
 380         [ 0 ..   7]   NBD_OPTS_MAGIC
 381         [ 8 ..  11]   NBD option
 382         [12 ..  15]   Data length
 383         ...           Rest of request
 384
 385         [ 0 ..   7]   NBD_OPTS_MAGIC
 386         [ 8 ..  11]   Second NBD option
 387         [12 ..  15]   Data length
 388         ...           Rest of request
 389     */
 390
 391     if (nbd_negotiate_read(client->ioc, &flags, sizeof(flags)) !=
 392         sizeof(flags)) {
 393         LOG("read failed");
 394         return -EIO;
 395     }
 396     TRACE("Checking client flags");
 397     be32_to_cpus(&flags);
 398     if (flags & NBD_FLAG_C_FIXED_NEWSTYLE) {
 399         TRACE("Client supports fixed newstyle handshake");
 400         fixedNewstyle = true;
 401         flags &= ~NBD_FLAG_C_FIXED_NEWSTYLE;
 402     }
 403     if (flags != 0) {
 404         TRACE("Unknown client flags 0x%" PRIx32 " received", flags);
 405         return -EIO;
 406     }
 407
 408     while (1) {
 409         int ret;
 410         uint32_t clientflags, length;
 411         uint64_t magic;
 412
 413         if (nbd_negotiate_read(client->ioc, &magic, sizeof(magic)) !=
 414             sizeof(magic)) {
 415             LOG("read failed");
 416             return -EINVAL;
 417         }
 418         TRACE("Checking opts magic");
 419         if (magic != be64_to_cpu(NBD_OPTS_MAGIC)) {
 420             LOG("Bad magic received");
 421             return -EINVAL;
 422         }
 423
 424         if (nbd_negotiate_read(client->ioc, &clientflags,
 425                                sizeof(clientflags)) != sizeof(clientflags)) {
 426             LOG("read failed");
 427             return -EINVAL;
 428         }
 429         clientflags = be32_to_cpu(clientflags);
 430
 431         if (nbd_negotiate_read(client->ioc, &length, sizeof(length)) !=
 432             sizeof(length)) {
 433             LOG("read failed");
 434             return -EINVAL;
 435         }
 436         length = be32_to_cpu(length);
 437
 438         TRACE("Checking option 0x%" PRIx32, clientflags);
 439         if (client->tlscreds &&
 440             client->ioc == (QIOChannel *)client->sioc) {
 441             QIOChannel *tioc;
 442             if (!fixedNewstyle) {
 443                 TRACE("Unsupported option 0x%" PRIx32, clientflags);
 444                 return -EINVAL;
 445             }
 446             switch (clientflags) {
 447             case NBD_OPT_STARTTLS:
 448                 tioc = nbd_negotiate_handle_starttls(client, length);
 449                 if (!tioc) {
 450                     return -EIO;
 451                 }
 452                 object_unref(OBJECT(client->ioc));
 453                 client->ioc = QIO_CHANNEL(tioc);
 454                 break;
 455
 456             case NBD_OPT_EXPORT_NAME:
 457                 /* No way to return an error to client, so drop connection */
 458                 TRACE("Option 0x%x not permitted before TLS", clientflags);
 459                 return -EINVAL;
 460
 461             default:
 462                 TRACE("Option 0x%" PRIx32 " not permitted before TLS",
 463                       clientflags);
 464                 if (nbd_negotiate_drop_sync(client->ioc, length) != length) {
 465                     return -EIO;
 466                 }
 467                 ret = nbd_negotiate_send_rep(client->ioc, NBD_REP_ERR_TLS_REQD,
 468                                              clientflags);
 469                 if (ret < 0) {
 470                     return ret;
 471                 }
 472                 break;
 473             }
 474         } else if (fixedNewstyle) {
 475             switch (clientflags) {
 476             case NBD_OPT_LIST:
 477                 ret = nbd_negotiate_handle_list(client, length);
 478                 if (ret < 0) {
 479                     return ret;
 480                 }
 481                 break;
 482
 483             case NBD_OPT_ABORT:
 484                 return -EINVAL;
 485
 486             case NBD_OPT_EXPORT_NAME:
 487                 return nbd_negotiate_handle_export_name(client, length);
 488
 489             case NBD_OPT_STARTTLS:
 490                 if (nbd_negotiate_drop_sync(client->ioc, length) != length) {
 491                     return -EIO;
 492                 }
 493                 if (client->tlscreds) {
 494                     TRACE("TLS already enabled");
 495                     ret = nbd_negotiate_send_rep(client->ioc,
 496                                                  NBD_REP_ERR_INVALID,
 497                                                  clientflags);
 498                 } else {
 499                     TRACE("TLS not configured");
 500                     ret = nbd_negotiate_send_rep(client->ioc,
 501                                                  NBD_REP_ERR_POLICY,
 502                                                  clientflags);
 503                 }
 504                 if (ret < 0) {
 505                     return ret;
 506                 }
 507                 break;
 508             default:
 509                 TRACE("Unsupported option 0x%" PRIx32, clientflags);
 510                 if (nbd_negotiate_drop_sync(client->ioc, length) != length) {
 511                     return -EIO;
 512                 }
 513                 ret = nbd_negotiate_send_rep(client->ioc, NBD_REP_ERR_UNSUP,
 514                                              clientflags);
 515                 if (ret < 0) {
 516                     return ret;
 517                 }
 518                 break;
 519             }
 520         } else {
 521             /*
 522              * If broken new-style we should drop the connection
 523              * for anything except NBD_OPT_EXPORT_NAME
 524              */
 525             switch (clientflags) {
 526             case NBD_OPT_EXPORT_NAME:
 527                 return nbd_negotiate_handle_export_name(client, length);
 528
 529             default:
 530                 TRACE("Unsupported option 0x%" PRIx32, clientflags);
 531                 return -EINVAL;
 532             }
 533         }
 534     }
 535 }
 536
 537 typedef struct {
 538     NBDClient *client;
 539     Coroutine *co;
 540 } NBDClientNewData;
 541
 542 static coroutine_fn int nbd_negotiate(NBDClientNewData *data)
 543 {
 544     NBDClient *client = data->client;
 545     char buf[8 + 8 + 8 + 128];
 546     int rc;
 547     const int myflags = (NBD_FLAG_HAS_FLAGS | NBD_FLAG_SEND_TRIM |
 548                          NBD_FLAG_SEND_FLUSH | NBD_FLAG_SEND_FUA);
 549     bool oldStyle;
 550
 551     /* Old style negotiation header without options
 552         [ 0 ..   7]   passwd       ("NBDMAGIC")
 553         [ 8 ..  15]   magic        (NBD_CLIENT_MAGIC)
 554         [16 ..  23]   size
 555         [24 ..  25]   server flags (0)
 556         [26 ..  27]   export flags
 557         [28 .. 151]   reserved     (0)
 558
 559        New style negotiation header with options
 560         [ 0 ..   7]   passwd       ("NBDMAGIC")
 561         [ 8 ..  15]   magic        (NBD_OPTS_MAGIC)
 562         [16 ..  17]   server flags (0)
 563         ....options sent....
 564         [18 ..  25]   size
 565         [26 ..  27]   export flags
 566         [28 .. 151]   reserved     (0)
 567      */
 568
 569     qio_channel_set_blocking(client->ioc, false, NULL);
 570     rc = -EINVAL;
 571
 572     TRACE("Beginning negotiation.");
 573     memset(buf, 0, sizeof(buf));
 574     memcpy(buf, "NBDMAGIC", 8);
 575
 576     oldStyle = client->exp != NULL && !client->tlscreds;
 577     if (oldStyle) {
 578         assert ((client->exp->nbdflags & ~65535) == 0);
 579         TRACE("advertising size %" PRIu64 " and flags %x",
 580               client->exp->size, client->exp->nbdflags | myflags);
 581         stq_be_p(buf + 8, NBD_CLIENT_MAGIC);
 582         stq_be_p(buf + 16, client->exp->size);
 583         stw_be_p(buf + 26, client->exp->nbdflags | myflags);
 584     } else {
 585         stq_be_p(buf + 8, NBD_OPTS_MAGIC);
 586         stw_be_p(buf + 16, NBD_FLAG_FIXED_NEWSTYLE);
 587     }
 588
 589     if (oldStyle) {
 590         if (client->tlscreds) {
 591             TRACE("TLS cannot be enabled with oldstyle protocol");
 592             goto fail;
 593         }
 594         if (nbd_negotiate_write(client->ioc, buf, sizeof(buf)) != sizeof(buf)) {
 595             LOG("write failed");
 596             goto fail;
 597         }
 598     } else {
 599         if (nbd_negotiate_write(client->ioc, buf, 18) != 18) {
 600             LOG("write failed");
 601             goto fail;
 602         }
 603         rc = nbd_negotiate_options(client);
 604         if (rc != 0) {
 605             LOG("option negotiation failed");
 606             goto fail;
 607         }
 608
 609         assert ((client->exp->nbdflags & ~65535) == 0);
 610         TRACE("advertising size %" PRIu64 " and flags %x",
 611               client->exp->size, client->exp->nbdflags | myflags);
 612         stq_be_p(buf + 18, client->exp->size);
 613         stw_be_p(buf + 26, client->exp->nbdflags | myflags);
 614         if (nbd_negotiate_write(client->ioc, buf + 18, sizeof(buf) - 18) !=
 615             sizeof(buf) - 18) {
 616             LOG("write failed");
 617             goto fail;
 618         }
 619     }
 620
 621     TRACE("Negotiation succeeded.");
 622     rc = 0;
 623 fail:
 624     return rc;
 625 }
 626
 627 static ssize_t nbd_receive_request(QIOChannel *ioc, struct nbd_request *request)
 628 {
 629     uint8_t buf[NBD_REQUEST_SIZE];
 630     uint32_t magic;
 631     ssize_t ret;
 632
 633     ret = read_sync(ioc, buf, sizeof(buf));
 634     if (ret < 0) {
 635         return ret;
 636     }
 637
 638     if (ret != sizeof(buf)) {
 639         LOG("read failed");
 640         return -EINVAL;
 641     }
 642
 643     /* Request
 644        [ 0 ..  3]   magic   (NBD_REQUEST_MAGIC)
 645        [ 4 ..  7]   type    (0 == READ, 1 == WRITE)
 646        [ 8 .. 15]   handle
 647        [16 .. 23]   from
 648        [24 .. 27]   len
 649      */
 650
 651     magic = ldl_be_p(buf);
 652     request->type   = ldl_be_p(buf + 4);
 653     request->handle = ldq_be_p(buf + 8);
 654     request->from   = ldq_be_p(buf + 16);
 655     request->len    = ldl_be_p(buf + 24);
 656
 657     TRACE("Got request: { magic = 0x%" PRIx32 ", .type = %" PRIx32
 658           ", from = %" PRIu64 " , len = %" PRIu32 " }",
 659           magic, request->type, request->from, request->len);
 660
 661     if (magic != NBD_REQUEST_MAGIC) {
 662         LOG("invalid magic (got 0x%" PRIx32 ")", magic);
 663         return -EINVAL;
 664     }
 665     return 0;
 666 }
 667
 668 static ssize_t nbd_send_reply(QIOChannel *ioc, struct nbd_reply *reply)
 669 {
 670     uint8_t buf[NBD_REPLY_SIZE];
 671     ssize_t ret;
 672
 673     reply->error = system_errno_to_nbd_errno(reply->error);
 674
 675     TRACE("Sending response to client: { .error = %" PRId32
 676           ", handle = %" PRIu64 " }",
 677           reply->error, reply->handle);
 678
 679     /* Reply
 680        [ 0 ..  3]    magic   (NBD_REPLY_MAGIC)
 681        [ 4 ..  7]    error   (0 == no error)
 682        [ 7 .. 15]    handle
 683      */
 684     stl_be_p(buf, NBD_REPLY_MAGIC);
 685     stl_be_p(buf + 4, reply->error);
 686     stq_be_p(buf + 8, reply->handle);
 687
 688     ret = write_sync(ioc, buf, sizeof(buf));
 689     if (ret < 0) {
 690         return ret;
 691     }
 692
 693     if (ret != sizeof(buf)) {
 694         LOG("writing to socket failed");
 695         return -EINVAL;
 696     }
 697     return 0;
 698 }
 699
 700 #define MAX_NBD_REQUESTS 16
 701
 702 void nbd_client_get(NBDClient *client)
 703 {
 704     client->refcount++;
 705 }
 706
 707 void nbd_client_put(NBDClient *client)
 708 {
 709     if (--client->refcount == 0) {
 710         /* The last reference should be dropped by client->close,
 711          * which is called by client_close.
 712          */
 713         assert(client->closing);
 714
 715         nbd_unset_handlers(client);
 716         object_unref(OBJECT(client->sioc));
 717         object_unref(OBJECT(client->ioc));
 718         if (client->tlscreds) {
 719             object_unref(OBJECT(client->tlscreds));
 720         }
 721         g_free(client->tlsaclname);
 722         if (client->exp) {
 723             QTAILQ_REMOVE(&client->exp->clients, client, next);
 724             nbd_export_put(client->exp);
 725         }
 726         g_free(client);
 727     }
 728 }
 729
 730 static void client_close(NBDClient *client)
 731 {
 732     if (client->closing) {
 733         return;
 734     }
 735
 736     client->closing = true;
 737
 738     /* Force requests to finish.  They will drop their own references,
 739      * then we'll close the socket and free the NBDClient.
 740      */
 741     qio_channel_shutdown(client->ioc, QIO_CHANNEL_SHUTDOWN_BOTH,
 742                          NULL);
 743
 744     /* Also tell the client, so that they release their reference.  */
 745     if (client->close) {
 746         client->close(client);
 747     }
 748 }
 749
 750 static NBDRequest *nbd_request_get(NBDClient *client)
 751 {
 752     NBDRequest *req;
 753
 754     assert(client->nb_requests <= MAX_NBD_REQUESTS - 1);
 755     client->nb_requests++;
 756     nbd_update_can_read(client);
 757
 758     req = g_new0(NBDRequest, 1);
 759     nbd_client_get(client);
 760     req->client = client;
 761     return req;
 762 }
 763
 764 static void nbd_request_put(NBDRequest *req)
 765 {
 766     NBDClient *client = req->client;
 767
 768     if (req->data) {
 769         qemu_vfree(req->data);
 770     }
 771     g_free(req);
 772
 773     client->nb_requests--;
 774     nbd_update_can_read(client);
 775     nbd_client_put(client);
 776 }
 777
 778 static void blk_aio_attached(AioContext *ctx, void *opaque)
 779 {
 780     NBDExport *exp = opaque;
 781     NBDClient *client;
 782
 783     TRACE("Export %s: Attaching clients to AIO context %p\n", exp->name, ctx);
 784
 785     exp->ctx = ctx;
 786
 787     QTAILQ_FOREACH(client, &exp->clients, next) {
 788         nbd_set_handlers(client);
 789     }
 790 }
 791
 792 static void blk_aio_detach(void *opaque)
 793 {
 794     NBDExport *exp = opaque;
 795     NBDClient *client;
 796
 797     TRACE("Export %s: Detaching clients from AIO context %p\n", exp->name, exp->ctx);
 798
 799     QTAILQ_FOREACH(client, &exp->clients, next) {
 800         nbd_unset_handlers(client);
 801     }
 802
 803     exp->ctx = NULL;
 804 }
 805
 806 static void nbd_eject_notifier(Notifier *n, void *data)
 807 {
 808     NBDExport *exp = container_of(n, NBDExport, eject_notifier);
 809     nbd_export_close(exp);
 810 }
 811
 812 NBDExport *nbd_export_new(BlockBackend *blk, off_t dev_offset, off_t size,
 813                           uint32_t nbdflags, void (*close)(NBDExport *),
 814                           Error **errp)
 815 {
 816     NBDExport *exp = g_malloc0(sizeof(NBDExport));
 817     exp->refcount = 1;
 818     QTAILQ_INIT(&exp->clients);
 819     exp->blk = blk;
 820     exp->dev_offset = dev_offset;
 821     exp->nbdflags = nbdflags;
 822     exp->size = size < 0 ? blk_getlength(blk) : size;
 823     if (exp->size < 0) {
 824         error_setg_errno(errp, -exp->size,
 825                          "Failed to determine the NBD export's length");
 826         goto fail;
 827     }
 828     exp->size -= exp->size % BDRV_SECTOR_SIZE;
 829
 830     exp->close = close;
 831     exp->ctx = blk_get_aio_context(blk);
 832     blk_ref(blk);
 833     blk_add_aio_context_notifier(blk, blk_aio_attached, blk_aio_detach, exp);
 834
 835     exp->eject_notifier.notify = nbd_eject_notifier;
 836     blk_add_remove_bs_notifier(blk, &exp->eject_notifier);
 837
 838     /*
 839      * NBD exports are used for non-shared storage migration.  Make sure
 840      * that BDRV_O_INACTIVE is cleared and the image is ready for write
 841      * access since the export could be available before migration handover.
 842      */
 843     aio_context_acquire(exp->ctx);
 844     blk_invalidate_cache(blk, NULL);
 845     aio_context_release(exp->ctx);
 846     return exp;
 847
 848 fail:
 849     g_free(exp);
 850     return NULL;
 851 }
 852
 853 NBDExport *nbd_export_find(const char *name)
 854 {
 855     NBDExport *exp;
 856     QTAILQ_FOREACH(exp, &exports, next) {
 857         if (strcmp(name, exp->name) == 0) {
 858             return exp;
 859         }
 860     }
 861
 862     return NULL;
 863 }
 864
 865 void nbd_export_set_name(NBDExport *exp, const char *name)
 866 {
 867     if (exp->name == name) {
 868         return;
 869     }
 870
 871     nbd_export_get(exp);
 872     if (exp->name != NULL) {
 873         g_free(exp->name);
 874         exp->name = NULL;
 875         QTAILQ_REMOVE(&exports, exp, next);
 876         nbd_export_put(exp);
 877     }
 878     if (name != NULL) {
 879         nbd_export_get(exp);
 880         exp->name = g_strdup(name);
 881         QTAILQ_INSERT_TAIL(&exports, exp, next);
 882     }
 883     nbd_export_put(exp);
 884 }
 885
 886 void nbd_export_close(NBDExport *exp)
 887 {
 888     NBDClient *client, *next;
 889
 890     nbd_export_get(exp);
 891     QTAILQ_FOREACH_SAFE(client, &exp->clients, next, next) {
 892         client_close(client);
 893     }
 894     nbd_export_set_name(exp, NULL);
 895     nbd_export_put(exp);
 896 }
 897
 898 void nbd_export_get(NBDExport *exp)
 899 {
 900     assert(exp->refcount > 0);
 901     exp->refcount++;
 902 }
 903
 904 void nbd_export_put(NBDExport *exp)
 905 {
 906     assert(exp->refcount > 0);
 907     if (exp->refcount == 1) {
 908         nbd_export_close(exp);
 909     }
 910
 911     if (--exp->refcount == 0) {
 912         assert(exp->name == NULL);
 913
 914         if (exp->close) {
 915             exp->close(exp);
 916         }
 917
 918         if (exp->blk) {
 919             notifier_remove(&exp->eject_notifier);
 920             blk_remove_aio_context_notifier(exp->blk, blk_aio_attached,
 921                                             blk_aio_detach, exp);
 922             blk_unref(exp->blk);
 923             exp->blk = NULL;
 924         }
 925
 926         g_free(exp);
 927     }
 928 }
 929
 930 BlockBackend *nbd_export_get_blockdev(NBDExport *exp)
 931 {
 932     return exp->blk;
 933 }
 934
 935 void nbd_export_close_all(void)
 936 {
 937     NBDExport *exp, *next;
 938
 939     QTAILQ_FOREACH_SAFE(exp, &exports, next, next) {
 940         nbd_export_close(exp);
 941     }
 942 }
 943
 944 static ssize_t nbd_co_send_reply(NBDRequest *req, struct nbd_reply *reply,
 945                                  int len)
 946 {
 947     NBDClient *client = req->client;
 948     ssize_t rc, ret;
 949
 950     g_assert(qemu_in_coroutine());
 951     qemu_co_mutex_lock(&client->send_lock);
 952     client->send_coroutine = qemu_coroutine_self();
 953     nbd_set_handlers(client);
 954
 955     if (!len) {
 956         rc = nbd_send_reply(client->ioc, reply);
 957     } else {
 958         qio_channel_set_cork(client->ioc, true);
 959         rc = nbd_send_reply(client->ioc, reply);
 960         if (rc >= 0) {
 961             ret = write_sync(client->ioc, req->data, len);
 962             if (ret != len) {
 963                 rc = -EIO;
 964             }
 965         }
 966         qio_channel_set_cork(client->ioc, false);
 967     }
 968
 969     client->send_coroutine = NULL;
 970     nbd_set_handlers(client);
 971     qemu_co_mutex_unlock(&client->send_lock);
 972     return rc;
 973 }
 974
 975 /* Collect a client request.  Return 0 if request looks valid, -EAGAIN
 976  * to keep trying the collection, -EIO to drop connection right away,
 977  * and any other negative value to report an error to the client
 978  * (although the caller may still need to disconnect after reporting
 979  * the error).  */
 980 static ssize_t nbd_co_receive_request(NBDRequest *req,
 981                                       struct nbd_request *request)
 982 {
 983     NBDClient *client = req->client;
 984     uint32_t command;
 985     ssize_t rc;
 986
 987     g_assert(qemu_in_coroutine());
 988     client->recv_coroutine = qemu_coroutine_self();
 989     nbd_update_can_read(client);
 990
 991     rc = nbd_receive_request(client->ioc, request);
 992     if (rc < 0) {
 993         if (rc != -EAGAIN) {
 994             rc = -EIO;
 995         }
 996         goto out;
 997     }
 998
 999     TRACE("Decoding type");
1000
1001     command = request->type & NBD_CMD_MASK_COMMAND;
1002     if (command != NBD_CMD_WRITE) {
1003         /* No payload, we are ready to read the next request.  */
1004         req->complete = true;
1005     }
1006
1007     if (command == NBD_CMD_DISC) {
1008         /* Special case: we're going to disconnect without a reply,
1009          * whether or not flags, from, or len are bogus */
1010         TRACE("Request type is DISCONNECT");
1011         rc = -EIO;
1012         goto out;
1013     }
1014
1015     /* Check for sanity in the parameters, part 1.  Defer as many
1016      * checks as possible until after reading any NBD_CMD_WRITE
1017      * payload, so we can try and keep the connection alive.  */
1018     if ((request->from + request->len) < request->from) {
1019         LOG("integer overflow detected, you're probably being attacked");
1020         rc = -EINVAL;
1021         goto out;
1022     }
1023
1024     if (command == NBD_CMD_READ || command == NBD_CMD_WRITE) {
1025         if (request->len > NBD_MAX_BUFFER_SIZE) {
1026             LOG("len (%" PRIu32" ) is larger than max len (%u)",
1027                 request->len, NBD_MAX_BUFFER_SIZE);
1028             rc = -EINVAL;
1029             goto out;
1030         }
1031
1032         req->data = blk_try_blockalign(client->exp->blk, request->len);
1033         if (req->data == NULL) {
1034             rc = -ENOMEM;
1035             goto out;
1036         }
1037     }
1038     if (command == NBD_CMD_WRITE) {
1039         TRACE("Reading %" PRIu32 " byte(s)", request->len);
1040
1041         if (read_sync(client->ioc, req->data, request->len) != request->len) {
1042             LOG("reading from socket failed");
1043             rc = -EIO;
1044             goto out;
1045         }
1046         req->complete = true;
1047     }
1048
1049     /* Sanity checks, part 2. */
1050     if (request->from + request->len > client->exp->size) {
1051         LOG("operation past EOF; From: %" PRIu64 ", Len: %" PRIu32
1052             ", Size: %" PRIu64, request->from, request->len,
1053             (uint64_t)client->exp->size);
1054         rc = command == NBD_CMD_WRITE ? -ENOSPC : -EINVAL;
1055         goto out;
1056     }
1057     if (request->type & ~NBD_CMD_MASK_COMMAND & ~NBD_CMD_FLAG_FUA) {
1058         LOG("unsupported flags (got 0x%x)",
1059             request->type & ~NBD_CMD_MASK_COMMAND);
1060         return -EINVAL;
1061     }
1062
1063     rc = 0;
1064
1065 out:
1066     client->recv_coroutine = NULL;
1067     nbd_update_can_read(client);
1068
1069     return rc;
1070 }
1071
1072 static void nbd_trip(void *opaque)
1073 {
1074     NBDClient *client = opaque;
1075     NBDExport *exp = client->exp;
1076     NBDRequest *req;
1077     struct nbd_request request;
1078     struct nbd_reply reply;
1079     ssize_t ret;
1080     uint32_t command;
1081     int flags;
1082
1083     TRACE("Reading request.");
1084     if (client->closing) {
1085         return;
1086     }
1087
1088     req = nbd_request_get(client);
1089     ret = nbd_co_receive_request(req, &request);
1090     if (ret == -EAGAIN) {
1091         goto done;
1092     }
1093     if (ret == -EIO) {
1094         goto out;
1095     }
1096
1097     reply.handle = request.handle;
1098     reply.error = 0;
1099
1100     if (ret < 0) {
1101         reply.error = -ret;
1102         goto error_reply;
1103     }
1104     command = request.type & NBD_CMD_MASK_COMMAND;
1105
1106     if (client->closing) {
1107         /*
1108          * The client may be closed when we are blocked in
1109          * nbd_co_receive_request()
1110          */
1111         goto done;
1112     }
1113
1114     switch (command) {
1115     case NBD_CMD_READ:
1116         TRACE("Request type is READ");
1117
1118         if (request.type & NBD_CMD_FLAG_FUA) {
1119             ret = blk_co_flush(exp->blk);
1120             if (ret < 0) {
1121                 LOG("flush failed");
1122                 reply.error = -ret;
1123                 goto error_reply;
1124             }
1125         }
1126
1127         ret = blk_pread(exp->blk, request.from + exp->dev_offset,
1128                         req->data, request.len);
1129         if (ret < 0) {
1130             LOG("reading from file failed");
1131             reply.error = -ret;
1132             goto error_reply;
1133         }
1134
1135         TRACE("Read %" PRIu32" byte(s)", request.len);
1136         if (nbd_co_send_reply(req, &reply, request.len) < 0)
1137             goto out;
1138         break;
1139     case NBD_CMD_WRITE:
1140         TRACE("Request type is WRITE");
1141
1142         if (exp->nbdflags & NBD_FLAG_READ_ONLY) {
1143             TRACE("Server is read-only, return error");
1144             reply.error = EROFS;
1145             goto error_reply;
1146         }
1147
1148         TRACE("Writing to device");
1149
1150         flags = 0;
1151         if (request.type & NBD_CMD_FLAG_FUA) {
1152             flags |= BDRV_REQ_FUA;
1153         }
1154         ret = blk_pwrite(exp->blk, request.from + exp->dev_offset,
1155                          req->data, request.len, flags);
1156         if (ret < 0) {
1157             LOG("writing to file failed");
1158             reply.error = -ret;
1159             goto error_reply;
1160         }
1161
1162         if (nbd_co_send_reply(req, &reply, 0) < 0) {
1163             goto out;
1164         }
1165         break;
1166
1167     case NBD_CMD_DISC:
1168         /* unreachable, thanks to special case in nbd_co_receive_request() */
1169         abort();
1170
1171     case NBD_CMD_FLUSH:
1172         TRACE("Request type is FLUSH");
1173
1174         ret = blk_co_flush(exp->blk);
1175         if (ret < 0) {
1176             LOG("flush failed");
1177             reply.error = -ret;
1178         }
1179         if (nbd_co_send_reply(req, &reply, 0) < 0) {
1180             goto out;
1181         }
1182         break;
1183     case NBD_CMD_TRIM:
1184         TRACE("Request type is TRIM");
1185         ret = blk_co_pdiscard(exp->blk, request.from + exp->dev_offset,
1186                               request.len);
1187         if (ret < 0) {
1188             LOG("discard failed");
1189             reply.error = -ret;
1190         }
1191         if (nbd_co_send_reply(req, &reply, 0) < 0) {
1192             goto out;
1193         }
1194         break;
1195     default:
1196         LOG("invalid request type (%" PRIu32 ") received", request.type);
1197         reply.error = EINVAL;
1198     error_reply:
1199         /* We must disconnect after NBD_CMD_WRITE if we did not
1200          * read the payload.
1201          */
1202         if (nbd_co_send_reply(req, &reply, 0) < 0 || !req->complete) {
1203             goto out;
1204         }
1205         break;
1206     }
1207
1208     TRACE("Request/Reply complete");
1209
1210 done:
1211     nbd_request_put(req);
1212     return;
1213
1214 out:
1215     nbd_request_put(req);
1216     client_close(client);
1217 }
1218
1219 static void nbd_read(void *opaque)
1220 {
1221     NBDClient *client = opaque;
1222
1223     if (client->recv_coroutine) {
1224         qemu_coroutine_enter(client->recv_coroutine);
1225     } else {
1226         qemu_coroutine_enter(qemu_coroutine_create(nbd_trip, client));
1227     }
1228 }
1229
1230 static void nbd_restart_write(void *opaque)
1231 {
1232     NBDClient *client = opaque;
1233
1234     qemu_coroutine_enter(client->send_coroutine);
1235 }
1236
1237 static void nbd_set_handlers(NBDClient *client)
1238 {
1239     if (client->exp && client->exp->ctx) {
1240         aio_set_fd_handler(client->exp->ctx, client->sioc->fd,
1241                            true,
1242                            client->can_read ? nbd_read : NULL,
1243                            client->send_coroutine ? nbd_restart_write : NULL,
1244                            client);
1245     }
1246 }
1247
1248 static void nbd_unset_handlers(NBDClient *client)
1249 {
1250     if (client->exp && client->exp->ctx) {
1251         aio_set_fd_handler(client->exp->ctx, client->sioc->fd,
1252                            true, NULL, NULL, NULL);
1253     }
1254 }
1255
1256 static void nbd_update_can_read(NBDClient *client)
1257 {
1258     bool can_read = client->recv_coroutine ||
1259                     client->nb_requests < MAX_NBD_REQUESTS;
1260
1261     if (can_read != client->can_read) {
1262         client->can_read = can_read;
1263         nbd_set_handlers(client);
1264
1265         /* There is no need to invoke aio_notify(), since aio_set_fd_handler()
1266          * in nbd_set_handlers() will have taken care of that */
1267     }
1268 }
1269
1270 static coroutine_fn void nbd_co_client_start(void *opaque)
1271 {
1272     NBDClientNewData *data = opaque;
1273     NBDClient *client = data->client;
1274     NBDExport *exp = client->exp;
1275
1276     if (exp) {
1277         nbd_export_get(exp);
1278     }
1279     if (nbd_negotiate(data)) {
1280         client_close(client);
1281         goto out;
1282     }
1283     qemu_co_mutex_init(&client->send_lock);
1284     nbd_set_handlers(client);
1285
1286     if (exp) {
1287         QTAILQ_INSERT_TAIL(&exp->clients, client, next);
1288     }
1289 out:
1290     g_free(data);
1291 }
1292
1293 void nbd_client_new(NBDExport *exp,
1294                     QIOChannelSocket *sioc,
1295                     QCryptoTLSCreds *tlscreds,
1296                     const char *tlsaclname,
1297                     void (*close_fn)(NBDClient *))
1298 {
1299     NBDClient *client;
1300     NBDClientNewData *data = g_new(NBDClientNewData, 1);
1301
1302     client = g_malloc0(sizeof(NBDClient));
1303     client->refcount = 1;
1304     client->exp = exp;
1305     client->tlscreds = tlscreds;
1306     if (tlscreds) {
1307         object_ref(OBJECT(client->tlscreds));
1308     }
1309     client->tlsaclname = g_strdup(tlsaclname);
1310     client->sioc = sioc;
1311     object_ref(OBJECT(client->sioc));
1312     client->ioc = QIO_CHANNEL(sioc);
1313     object_ref(OBJECT(client->ioc));
1314     client->can_read = true;
1315     client->close = close_fn;
1316
1317     data->client = client;
1318     data->co = qemu_coroutine_create(nbd_co_client_start, data);
1319     qemu_coroutine_enter(data->co);
1320 }